Failed to overlay OSD with colors.

[duiniuluantanqin]

I want to overlay a text watermark onto a video using SDL_ttf, but failed. Below is my core code.

pl_map_avframe_ex
pl_swapchain_start_frame
pl_frame_from_swapchain

// above is some pseudocode 
... ...

TTF_Font *font = TTF_OpenFont("simsun.ttc", 24);
SDL_Color color = {255, 255, 255, 128};
SDL_Surface *text_surface = TTF_RenderUTF8_Blended(font , "osd_text", color);
upload_plane(text_surface, &osd_tex, &osd_plane);

struct pl_overlay osd;
struct pl_overlay_part osd_part;
if (osd_tex) {
    osd_part = (struct pl_overlay_part) {
        .src = { 0, 0, osd_tex->params.w, osd_tex->params.h },
        .dst = { 0, 0, osd_tex->params.w, osd_tex->params.h },
    };
    osd = (struct pl_overlay) {
        .tex        = osd_tex,
        .mode       = PL_OVERLAY_NORMAL,
        .repr       = image.repr,
        .color      = image.color,
        .coords     = PL_OVERLAY_COORDS_DST_FRAME,
        .parts      = &osd_part,
        .num_parts  = 1,
    };
    target.overlays = &osd;
    target.num_overlays = 1;
}

pl_render_image(renderer, image, target, &pl_render_default_params)

... ...
// below is some pseudocode 
pl_swapchain_submit_frame
pl_swapchain_swap_buffers

the function upload_plane is copy from demos\sdlimage.c

When I try to display white text, I get light purple instead. And other tests are shown below.
{255, 255, 255, 128} ----> expecting white but got light purple
{255, 0, 0, 0} ----> red
{0, 255, 0, 0} ----> expecting green but got blue.
{0, 0, 255, 0} ----> expecting blue but got green.

Also, I tried adjusting the order of the four variables below, but it still failed.
uint64_t masks[4] = { fmt->Rmask, fmt->Gmask, fmt->Bmask, fmt->Amask };